All-polymer photodetectors with photomultiplication

Abstract

All-polymer photodetectors (all-PPDs) are successfully fabricated with two polymers P3HT and PZ1 as active layers. The weight ratio of P3HT to PZ1 and the self-assembly time of the active layers were step-by-step optimized to improve the performance of the all-PPDs. The photomultiplication (PM) phenomenon is achieved in the all-PPDs with an external quantum efficiency (EQE) over 100% in the whole response range. The EQE values of the optimized PM type all-PPDs can be greatly improved with a bias increase. The EQE values are increased to 46 700% at 375 nm and 31 700% at 615 nm under a −20 V bias. The working mechanism of the PM type all-PPDs is hole tunneling injection from an external circuit assisted by interfacial trapped photogenerated electrons in P3HT/PZ1/P3HT. The specific detectivity (D*) values are improved to 5.6 × 10¹² Jones at 375 nm and 6.1 × 10¹² Jones at 615 nm under a −20 V bias. The relatively large D* can be attributed to the enhanced hole tunneling injection under light illumination conditions and the relatively low dark current density.